Mastodon is described as 'decentralized microblogging engine. FEATURES - Free and open-source. - Decentralized, no worries about a single company controlling your communications. - Supports the standardized ActivityPub protocol - Fully interoperable with' and is a very popular Social Network in the Social & Communications category. There are more than 100 alternatives to Mastodon for a variety of platforms, including Online / Web-based, Android, iPhone, Self-Hosted solutions and iPad. Most alternatives are Social Networks and Microblogs. The best alternative is Diaspora, which is both free and Open Source. Other great apps like Mastodon are Twitter (Free), Pixelfed (Free, Open Source), Gab (Freemium, Open Source) and Minds (Freemium, Open Source).